On the gravitational stability and mass estimation of stellar disks

Abstract

We estimate the masses of disks of galaxies using the marginal gravitational stability criterion and compare them with the photometrical disk mass evaluations. The comparison reveals that the stellar disks of most of spiral galaxies we considered cannot be substantially overheated (at least within several radial scalelengths) and are therefore unlikely to have experienced a significant merging event in their history. However, for substantial part of S0- type galaxies a stellar velocity dispersion is well in excess of the gravitational stability threshold suggesting a major merger event in the past. For four low surface brightness galaxies we found that the disk masses corresponding to the marginal stability condition are significantly higher than it may be expected from their brightness. Either their disks are dynamically overheated, or they contain a large amount of non-luminous matter.